Dupont Co. filed a patent application concerning pigmented ink for ink-jet (U.S. Pat. No. 5,519,085). In this patent, trimethylsilyl metacrylate, 2-phenylethyl metacrylate and ethoxytriethyleneglycol metacrylate were added dropwise to a tetrahydrofuran solution wherein 1-methoxy-1-trimethylsiloxy-2-methyl-1-propene and tetrabutylammoniumbiacetate are dissolved together to synthesize poly(metacrylic acid-co-2-phenylethyl metacrylate-co-ethoxytriethyleneglycol metacrylate) as the desired polymeric triblock copolymer, which is then dissolved in an aqueous potassium hydroxide solution to give a dispersant solution. Further, this dispersant solution and the corresponding pigment may be dispersed under high pressure to provide a stable dispersant solution, to which a variety of additives may be added to prepare ink for ink-jet.
However, the process described in the above patent is very complicated and also has a disadvantage that cost competitiveness is not good because the expensive raw materials are used for preparing ink for ink-jet.